What happened
On June 13, 1969, a flight instructor and a student pilot were conducting aerobatic training maneuvers near the Speck-Fehraltorf airfield. The flight involved a Beagle-Pup B.121-150, registration HB-NAH. After successfully performing several loops, the student pilot initiated a left-hand spin. The instructor noted that the entry was unusually abrupt, likely due to the student's attempt to correct previous criticism regarding her control inputs.
As the aircraft entered the spin, it began rotating rapidly and vertically without oscillation. The instructor attempted several recovery techniques, including applying opposite rudder and pushing the control column forward, but the rotation speed increased rather than decreased. The aircraft eventually crashed into a wooded area near Freudwil, resulting in one fatality (the student pilot) and one serious injury (the instructor). The aircraft was destroyed.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) conducted the inquiry in collaboration with the Zurich Cantonal Police. Investigators examined the aircraft's maintenance records, flight logs, and weight and balance configurations. The investigation confirmed that the aircraft was properly maintained and that the center of gravity was within the required limits for aerobatic flight.
To understand the flight dynamics, experts conducted reconstruction flight tests in October 1969. These tests involved performing approximately 40 spins to simulate the accident conditions. The testing demonstrated that the recovery procedures outlined in the Beagle-Pup Owner's Handbook—applying full opposite rudder, pausing, and then easing the control column forward—were effective in stopping the rotation, even following an abnormal entry.
Findings
- The primary cause of the accident was that the spin initiated by the student pilot could not be recovered in time by the instructor.
- The student's abrupt control inputs during the spin entry created an abnormal rotation that the instructor failed to neutralize.
- It is possible that the instructor did not wait long enough during the recovery sequence before attempting subsequent corrective measures.
- There was no evidence of mechanical failure or technical defects in the aircraft's controls or engine.